Electrochemical synthesis of chemicals offers many advantages over conventional methods (e.g., in product purity, effluent control and process simplicity) but certain problems frequently offset these advantages. One problem common to several electrosynthetic processes is that of electrode deactivation or poisoning. A case in point occurs in the anodic oxidation of arsenic (III) oxide to arsenic (V) acid. Within seconds of applying a given potential to the anode (oxidation electrode), the current density typically drops to a few percent of its initial value. Similarly, under constant current conditions, the anode potential rises rapidly and most of the current is consumed by side reactions (mainly O.sub.2 evolution).
Electrode deactivation can be avoided by conducting the electrolysis in the presence of a catalytic amount of a halide. However, the removal of the halide remaining in the product solution is a problem. One may consider using an ion exchange resin technique or electrochemical oxidation of halide to halogen. If one uses an ion exchange resin, the desired product is removed with the halide. Electrochemical oxidation of halide to halogen has the disadvantage that the current density and efficiency are reduced as the halide conversion proceeds.